1. Field of the Invention
The present invention relates generally to closing wheel assemblies for agricultural planters. In particular, the present invention relates to improved pivot assemblies for mounting closing wheel frames to planters.
2. Description of the Prior Art
The first “modern” planter was the John Deere 7000 series planter introduced in 1973. This planter is depicted in FIGS. 1, 2 and 3 of the accompanying drawings. This design utilized two opener disks 11 which contact at one point 12 and diverge at a small angle to form a furrow 13 in the ground. The depth of the furrow is determined by the adjustable position of the gauge wheels 14. The seed is dropped into a seed tube 15 and falls into the furrow 13.
A pair of closing wheels 16, which are mounted at an angle and are spring loaded to exert a downward force on the ground, then close the furrow 13 thereby covering the seed with soil. The closing wheels 16 are supported by a closing wheel frame 17. The closing wheel frame 17 was constructed from 0.164″ thick sheet metal for many years until the introduction of the John Deere 1700 series planter.
The closing wheel frame 17 on the original John Deere 7000 series planter was attached to the shank assembly 18 at a pivot point 19. The pivot point 19 on each side of the closing wheel frame 17 consisted of a heat-treated 0.750″ diameter bushing 20 (FIG. 3) clamped to the shank assembly 18 and the support casting 21 by a bolt 29 going through holes 22 in the shank assembly 18 and support casting 21. The outer bearing surface was a slightly larger than 0.750″ hole 23 in the sheet metal of the closing wheel frame 17.
Down pressure for the closing wheels 16 was provided by an extension spring attached at 24 to the support casting 21. The spring pressure was adjusted by a bolt 25. Because the moment arm 26 of the spring about the pivot point 19 was small relative to the moment arm 27 of the wheel reaction 28, the spring pressure was necessarily large. This resulted in high pressure on the bearing surfaces of the bushing 20 and the sheet metal hole 23, which in turn resulted in accelerated wear on both the bushing 20 and the hole 23.
Uneven wear on those components resulted in the closing wheels 16 pulling to one side and prevented them from closing the furrow 13 adequately. To alleviate this problem, John Deere increased the size of the bushing 20 to 1.00″ and changed the holes 22 to horizontal slots to allow the frame 17 to be adjusted to center the closing wheels 16 on the furrow 13. The slots were ineffective because by the time adjustment was needed, the parts obviously were worn which made it impossible to accurately relocate the bushings.
John Deere remedied this situation when they introduced the Model 7200 series planter in 1984. The bearing surface was increased to 1.562″ diameter, and a cam was introduced on the right-hand side. To accommodate these changes the new support casting was attached with two vertical bolts that go through holes in the top of the casting. The above changes did not adequately alleviate the problem and in 1992 John Deere changed the rear hole in the top of the support casting to a lateral slot to allow more adjustment.
With the introduction of the Model 1700 series planters, John Deere improved the closing wheel frame pivot by increasing the frame bearing surface to 0.25″ width and making it a casting. However, the thicker bearing surface and using steel on cast iron has not proven to be a major improvement over the earlier design.
Other manufacturers have experienced wear problems at the closing wheel frame pivot similar to John Deere but have basically stayed with a steel on steel bearing surface and have provided cams for adjustment. Several after-market repair kits have been available in recent years. Montezuma Welding and R K Products Inc. have provided a heat treated 0.250″ thick outer bearing surface along with heat treated cams. May-Wes Manufacturing Inc. markets a bushing kit (PERMA-FIX™) that provides a substantial wear surface as well as the means for lubrication. A&T Enterprises offers a repair kit (PRESS FIX™) that utilizes ball bearings mounted in conventional “flangette” mountings. The flangette mountings allow for misalignment and still allow the bearing outer race to be clamped tightly. The bearing used has a 1.00″ diameter bore that permits the use of a cam adjuster.